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Gratings & Accessories

Efficiency Characteristics of Diffraction Gratings
Efficiency and its variation with wavelength and spectral order are important characteristics of a diffraction grating. For a reflection grating, efficiency is defined as the energy flow (power) of monochromatic light diffracted into the order being measured, relative either to the energy flow of the incident light (absolute efficiency) or to the energy flow of specular reflection from a polished mirror substrate coated with the same material (relative efficiency). [Intensity may substitute for energy flow in these definitions.] Efficiency is defined similarly for transmission gratings, except that an uncoated substrate is used in the measurement of relative efficiency.

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Differences Between Ruled and Holographic Gratings
Due to the distinctions between the fabrication processes for ruled and holographic gratings, each type of grating has advantages and disadvantages relative to the other, some of which are described in this technical note.

View this tech note from the Newport Corporation Grating Handbook
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Handling Gratings
A diffraction grating is a first surface optic, so its surface cannot be touched or otherwise come in contact with another object without damaging it and perhaps affecting its performance. Damage can take the form of contamination (as in the adherence of finger oils) or distortion of the microscopic groove profile in the region of contact. This note describes the reasons why a grating must be handled carefully and provides guidelines for doing so.

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Testing and Characterizing Diffraction Gratings
It is fundamental to the nature of diffraction gratings that errors are relatively easy to measure, although not all attributes are equally detectable or sometimes even definable.

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The Physics of Diffraction Gratings
THE GRATING EQUATION
When monochromatic light is incident on a grating surface, it is diffracted into discrete directions. We can picture each grating groove as being a very small, slit-shaped source of diffracted light. The light diffracted by each groove combines to form set of diffracted wavefronts. The usefulness of a grating depends on the fact that there exists a unique set of discrete angles along which, for a given spacing d between grooves, the diffracted light from each facet is in phase with the light diffracted from any other facet, leading to constructive interference.

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Instructions for Adding or Interchanging Gratings in SpectraPro Spectrometers
If it becomes necessary to add or interchange gratings in the SpectraPro series of spectrometers, a specific procedure is recommended. This procedure should be done only by personnel familiar with handling delicate optical components and familiar with the alignment of optical instruments.

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Instructions for Adding or Interchanging Gratings in SpectraPro Spectrometers
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> spectroscopy

spectroscopy

Intensified CCD Imaging and spectroscopy Unravel the Mysteries of Carbon Nanotube Formation
Carbon nanotubes are hollow, cylindrical tubes formed by single layers of carbon atoms. They can be one atom layer thick (single-wall nanotube, or SWNT) or multiple layers thick (MWNT) with additional graphene layers forming concentrically aligned cylinders. SWNTs are formed by laser vaporization, dc-arc vaporization, chemical vapor deposition, or gas disproportionation in the presence of metal catalyst nanoparticles in background gases. Recently, SWNTs were formed by annealing C60 and Ni films in vacuum. SWNTs are another allotrope of solid carbon, joining the family of graphite, diamond, and solid fullerenes. They are the latest discovery in the field of carbon nanomolecules that began in the 1980s with the discovery of "Buckyballs", symmetrical carbon-atom spheres (named Buckminsterfullerenes) that resemble soccer balls. Like other carbon allotropes, the distinct characteristics of SWNTs are conveyed by the propensity of carbon atoms to bond to one another and form the ubiquitous planar hexagonal rings, as in graphite or the benzene molecule.

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Intensified CCD Imaging and spectroscopy Unravel the Mysteries of Carbon Nanotube Formation
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Measurement of Environmental Contaminant Hydrocarbons by Fluorescence spectroscopy
Polycyclic aromatic hydrocarbons (PAH) and related chemicals are the largest known class of mutagens and carcinogens. They are frequent components of environmental contamination in water and soil. Contamination levels often occur in the ppm range, well above current EPA standards for acceptable levels, which are in the ppb range. This note describes the novel combined use of standard UV spectroscopy and fluorescence excitation-emission spectroscopy to measure low ppm levels of PAH and other hydrocarbons. Standard Princeton Instruments spectroscopy components were used in a unique single system for both types of measurements. The results demonstrate that the two methods are complementary and that analysis of fluorescence excitation-emission matrices (EEM) of environmental contaminant hydrocarbons can sometimes provide greater sensitivity than UV spectroscopy.

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Measurement of Environmental Contaminant Hydrocarbons by Fluorescence spectroscopy
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Additive and Subtractive Modes of TriVista
The TriVista spectrometer can be used in single, double and triple configurations. Single configuration (Fig 1A) means all three stages can be used simultaneously and independently for three different projects. This is highly practical but quite rare situation. The most often TriVista is utilized as a double or triple system (Fig 1B,C) when light beam is passed sequentially through 2 or 3 stages and gratings of the involved stages coherently move together with very high precision. Two most common reasons why people use double or triple system instead of a single spectrometer ar high spectral resolution and high stray light rejection. These two effects can be achieved in different modes of TriVista operation...

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Additive and Subtractive Modes of TriVista
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BALF Research with Raman spectroscopy
The development of extremely sensitive CCD detectors and holographic-notch filters is fueling a resurgence in the field of Raman spectroscopy, particularly in the study of organic structures. Traditionally, using Raman spectroscopy to investigate living systems was hampered in two ways: its inability to detect very low-level signals (<10-9/10-12) from the excitation source, and the high stray-light levels in monochromators that masked low-frequency components in proximity to excitation wavelengths. With the more powerful and precise equipment available today, Raman spectroscopy has overcome these problems and is well suited even for the study of complex organic compounds. This note describes the landmark use of Raman vibrational spectroscopy to compare bronchoalveolar lavage fluid (BALF) of normal and alveolar proteinosis (AP) lungs.

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BALF Research with Raman spectroscopy
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Selecting the Right ICCD Camera!
This technical note is intended to help the researchers make the best selection of ICCD cameras for
low light time resolved imaging and spectroscopy applications. It briefly describes the benefits and
trade-offs involved with the various components of the system including intensifier type, CCD
resolution and frame rate. For more detailed information on intensifiers and gated ICCD technology,
please refer to the technical notes "Introduction to Image Intensifiers for Scientific Imaging", "ICCD
Gating" and "Comparison of Lens-Coupled and Fiber-Coupled ICCD cameras"

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Selecting the Right ICCD Camera!
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The Merits of Various Types of CCDs for spectroscopy Applications
High-end commercial CCDs can provide excellent sensitivity and detection limits for spectroscopy applications. Choosing the correct detector for an application requires an understanding of the basic device parameters involved and of how they affect a real experimental setup. The first step is to clarify the difference between detection limit and sensitivity.

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The Merits of Various Types of CCDs for spectroscopy Applications
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Raman spectroscopy Basics
Raman spectroscopy is a spectroscopic technique based on inelastic scattering of monochromatic light, usually from a laser source. Inelastic scattering means that the frequency of photons in monochromatic light changes upon interaction with a sample. Photons of the laser light are absorbed
by the sample and then reemitted. Frequency of the reemitted photons is shifted up or down in
comparison with original monochromatic frequency, which is called the Raman effect. This shift
provides information about vibrational, rotational and other low frequency transitions in molecules.
Raman spectroscopy can be used to study solid, liquid and gaseous samples.

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Raman spectroscopy Basics
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Real-Time Xylene Isomer Quantification Using Chemometric Raman Analysis
Raman spectroscopy has been used more in recent years due to the convergence of several technologies: CCD detection systems with high sensitivity in the NIR, small powerful diode-based lasers, and fiberoptic probes with integrated laser-and-signal filtering. These products, along with high-aperture short-focal-length spectrographs, provide quality Raman spectra with low fluorescence interference in compact, easy-to-use packages.

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Real-Time Xylene Isomer Quantification Using Chemometric Raman Analysis
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Confocal Raman Microscopy - General Overview
Origins – a battle with scattered light

The first confocal scanning microscope was invented in 1955 and patented in 1957 by the Harvard graduate Marvin Minsky. He was obsessed with resolving the mystery of the human nerve system anatomy which aids in performing an outstandingly complex set of cognitive functions. Though at that time the common shapes of nerve cells were generally known, the connection schemes between them were not mapped. The critical obstacle was that the tissue of the central nervous system was solidly packed with interwoven parts of cells. Individual cells were practically indistinguishable from each other by conventional wide-field optical microscopy because of the excessive scattered light blurring the image.

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Confocal Raman Microscopy - General Overview
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Optimizing Your NIR spectroscopy Setup
High-sensitivity, low-noise Princeton Instruments OMA V™ InGaAs detectors have been engineered to take full advantage of wellestablished spectrometer and laser technologies. The spectral range afforded by these 1.7-µm and 2.2-µm detectors reduces biofluorescence and increases the penetration depth for applications such as quantum dot luminescence, fluorescence, and NIR Raman.

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Optimizing Your NIR spectroscopy Setup
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Raman on SiGe Superlattice using TriVista
Si-SixGe1-x superlattices are usually grown in Chemical Vapor Deposition (CVD) or Physical Vapor Deposition (PVD) process by depositing nanometer-thick alternating layers of pure Si and SixGe1-x alloy on top of the silicon substrate. Uniformity of layer thickness is a critical parameter governing the unique superlattice properties, crucial in the development of microelectronic and optoelectronic devices as well as low –dimensional thermoelectric and thermionic devices. Available structural characterization methods include TEM, STM, XRD and Raman. The latter was found to be the most suitable for the express-analysis of the Si-SixGe1-x structural quality in laboratory environment because of less sample preparation required and lower equipment cost

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Raman on SiGe Superlattice using TriVista
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Time-Resoved Fluorescence spectroscopy
Normal fluorescence is useful as a highly selective and sensitive non-invasive probe. However, better chemical information can be gained from the same experiment. While normal fluorescence spectroscopy is useful as a highly selective and sensitive non-invasive probe, better chemical information can often be gained from the same experiment by exploiting the time-dependent nature of fluorescence.

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Time-Resolved Fluorescence spectroscopy
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Comparison of Lens-Coupled and Fiberoptic-Coupled ICCD Cameras
Many intensified CCD (ICCD) camera users are interested in the relative merits and demerits of lens-coupled and fiberoptic-coupled ICCDs. This technical note compares a variety of features of these high-performance cameras, concentrating primarily on camera sensitivity and signal-to-noiseratio (SNR) performance.

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Comparison of Lens-Coupled and Fiberoptic-Coupled ICCD Cameras

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> spectroscopy > Raman

Raman

> Spectrographs & Monochromators

Spectrographs & Monochromators

> Spectrographs & Monochromators > SpectraPro - Spectrographs & Monochromators

SpectraPro - Spectrographs & Monochromators

> spectroscopy Cameras

spectroscopy Cameras

Key Advantages of PI CCDs: Full Well Capacity

Each pixel on a CCD array represents a 3D potential well in Si material which can store electric charge, or electrons. The amount of electrons an individual pixel can store prior to saturation is known as “full well capacity.”

Is it better to have larger storage? The answer depends on what you are trying to achieve. Larger full well capacity adds protection against CCD pixel saturation, making it excellent for intense light applications such as characterizing laser lines or studying bright plasmas. On the other hand, large well capacity reduces the CCD’s quantitative abilities, causing image smearing in a phenomenon known as “blooming”. Therefore, for precise quantitative measurements and low-light applications like conventional Raman spectroscopy, full well capacity should be kept relatively small.

The situation can become even more complicated since individual pixels in theCCD imaging area, horizontal serial register and read-out node have three different values of full well capacity. To avoid confusion and complications PI/Acton provides its high performance CCD detectors with a unique Dual Capacity design. These detectors have a full well capacity with area pixels optimized for a wide range of applications, while a single read-out node with fixed capacity is substituted with dual readout amplifiers. While the capacity of one amplifier is optimized for low-light applications, the capacity of the other can handle very intense signals.

PI/Acton provides an experimentally-measured full well capacity value with each detector sold. During measurements, detector gain is adjusted so that the full range of the 16 bit ADC equals the single-pixel linear full well capacity of the CCD at 1x gain. At this gain, one photoelectron is converted into one Arbitrary Digital Unit (ADU), or one count. Since the CCD is often used as a radiometric detector in order to produce quantitative results, only the linear range of the full well capacity is employed. As a result, the full well capacities of PI/Acton detectors may be slightly lower than those found in the data sheets of other CCD manufacturers, so as to ensure a high level of linearity.

CCD Pixel Size (µm) Typical Full Well

Kodak KAF1400 6.8 x 6.8 45,000 e-

E2V CCD37-10 15 x 15 165,000 e-

Kodak KAF1000 24 x 24 630,000 e-

Key Advantages of PI CCDs: XP Cooling

Long Exposure Times

Low light applications including Raman spectroscopy or astronomical observations of remote stars require exposure times long enough for a CCD to accumulate enough photoelectrons from the incoming signal. At the same time, the CCD’s Si material produces “dark” electrons, which are mixed with the photoelectrons, subsequently spoiling the signal quality. Reducing the temperature of a CCD detector exponentially decreases the rate of “dark” electron generation and plays a crucial role in quantitative spectroscopy applications and scientific imaging.

Convenience

Deep cooling is typically achieved through the use of thermoelectric devices (TE), liquid nitrogen (LN), or external cryogenic compressors (CC). With liquid nitrogen and cryogenic compressor cooling capabilities, CCD detectors can reach extremely low temperatures, usually around -120C. The associated maintenance of compressor equipment as well as the daily refilling of liquid nitrogen makes them inconvenient and sometimes impossible to work with. PI/Acton’s XP cooling detectors utilize thermoelectric cooling and can reach temperatures down to -85C without any additional liquid assistance. If your application does not require exposure times of more than half an hour, these CCD temperature levels are enough to fully suppress dark noise below the detection limit.

Lifetime Vacuum Guarantee

XP technology reduces the vacuum chamber around the CCD, keeping thermal load and outgassing to a minimum, while a “getter” material absorbs any residual outgassing. A Peltier thermoelectric cooler maintains low temperatures within the CCD and stabilizes a control point to reduce dark current variation. A “feedback” circuit sustains +/- .05 C stability over a broad temperature range (+20 to -85°C for Spec-10 XP models; +20 to -75°C for PhotonMAX and VersArray). Before assembly, vacuum parts are kept in “dry” containers while processing is achieved via oil-less “molecular” pumps in order to ensure top design. Seals are consistently inspected for leaks and each device is systematically inspected for flaws. Thanks to the latest metal sealing materials, the vacuum is guaranteed for the lifetime of the camera, so re-pumping the camera every few years is no longer necessary.

Availability

Exclusive XP technology is available through PIXIS®, VersArray® XP, (imaging) and Spec-10® (spectroscopy) product lines from PI/Acton. Dark current rates of 0.001 to 0.002 e-/p/s, along with system read noise as low as <1 e-rms for the PhotonMAX and 2.5 to 2.6 e- rms for the VersArray and Spec:10 provide an excellent sensitivity.

Key Advantages of PI CCDs - Linearity
The conversion of photonic input to electronic output is the fundamental process that occurs in CCD sensors. During this process, photons incident on the CCD will be converted to electron/hole pairs while the electrons will be captured under the gate electrodes of the CCD. These electrons are then transferred in a "bucket brigade" fashion to the output amplifier where the charge is converted to a voltage output signal. An analog processing chain further amplifies this signal before it is finally digitized and transferred to a host computer for display, image processing and/or storage. The transfer function between the incident photonic signal and the final digitized output should vary linearly with the amount of light incident on the CCD. Hence, non-linearity is a measure of the deviation from the following relationship:

Digital Signal = Constant x Amount of Incident Light

High-performance PI/Acton CCD detectors exhibit exceptional linearity, which is extremely important in image and spectral analysis, including arithmetic ratios, shading correction, flat fielding, linear transforms, etc. Deviations from linearity in PI/Acton cameras are often less than a few tenths of a percent for over five orders of magnitude. This is far superior to video CCDs and other solid-state sensors which can exhibit non-linearity of several percent or more. For quantitative imaging, linearity is a stringent requirement. In our specifications we foresee the worse case scenario where the linearity could be equal or better then 1% over the whole dynamic range of a CCD.

There is no standard method for measuring or reporting linearity values. Typically, the numbers are reported as percent deviations from linearity. In our method, we plot the mean signal value versus the exposure time over the full dynamic range (full-well) of the CCD. A linear least-squares regression can then be fitted to the data. The deviation of each point from the calculated line gives a measure of the non-linearity of the system. The non-linearity can be reported as the sum of the maximum and minimum deviation divided by the maximum signal as a percentage:

Typical linearity plot of PIActon detector (non-linearity is 0.4%).

Key Advantages of PI CCDs: Optical Windows on PI Detectors

Before striking the CCD chip, light must travel through a transparent optical window. This window is absolutely necessary as the only physical barrier between the deep vacuum surrounding the CCD chip and the ambient air. Otherwise, CCD chips cooled to -80C or even -120C would immediately condense and produce excessive moisture. Also, a small portion of light from the optical window gets lost. Because PI/Acton engineers understand the value of each photon in the signal to researchers and industrial users, we provide the highest quality optical windows available in order to minimize signal losses. Also, unlike many other manufacturers, we offer a design with just a single input window.

Window Material
PI/Acton uses Grade 1 quartz windows in most of its cameras. This provides excellent transmission over the whole spectrum from 190 to 1100 nm. For operation at other wavelengths, such as vacuum UV, windows can be provided that are made of materials like MgFl 2.

Window Defects and Dust

PI/Acton uses the highest grade surface finish available for its windows. This minimizes the number and size of pits, scratches, and other defects to a point that they cannot normally be detected, even with sensitive CCD arrays. However, even minute defects can become visible under some illumination conditions, including very high f/# optics, parallel and coherent light. Under these circumstances some imperfections may be detected in a flatfield image. When necessary, flatfield correction software can generally remove these low level artifacts from digitized images. Sometimes very small dust particles from the atmosphere can sediment on the optical window and appear as small, shadow-like disks on the image.

Antireflection (A/R) Coatings

Each time light passes through an abrupt change in a refractive index, some fraction of it gets reflected. With uncoated quartz windows, about 3.5% of the light is reflected at each surface. To minimize reflections, antireflection (AR) coatings should be added to one or both sides of the input window.

PI/Acton offers four A/R coating options: three multilayer coatings optimized for relatively narrow spectral ranges (UV/AR, VIS/AR, NIR/AR), and one single layer MgFl 2 coating which reduces reflections over a broad spectral range (MG/FL). The reflected portion of incoming light for each of these coatings (in percents-per-surface) is illustrated in the figure below. Note that while each of the multilayer coatings achieves very low reflection in its intended spectral range, the amount of reflection is actually worse than no coating at all when operating outside the intended range. Therefore, coatings should be chosen with careful consideration. In many cases the broadband single layer coating should be considered first.

Portion of the light reflected from each surface of the uncoated window and window coated with UV/AR ,VIS/AR, NIR/AR and MgFl2.

Wedged Windows

The two surfaces of the window are near parallel. Therefore, each window may act as an imperfect etalon if used with coherent light. This can lead to interference fringes appearing in an image. While the magnitude of these fringes will be fairly small (particularly with an optimized A/R coating), the sensitive cooled CCD detector with high dynamic range can often detect them. To prevent this effect, PI/Acton can provide cameras with slightly wedge-shaped windows. In addition, we can apply custom A/R coatings. If you are considering a camera for imaging coherent light, contact one of our optical specialists to discuss the optimum design for your application.

Key Advantages of PI CCDs - CCD Grading and Defect Specfications

CCD sensor manufacturers grade their devices according to the number and type of defective pixels within them. A CCD sensor is a large cost component in the CCD detector. Therefore, choosing a sensor grade is an important consideration. CCDs with fewer defects naturally lower the manufacturing yield, thus increasing the cost. Unfortunately each CCD manufacturer uses a different scheme to grade devices. Grading schemes typically run from a grade 0 device, designating the highest quality available (nominally defect-free), to grade 1, 2, or 3, with the number of defects increasing with the grade number.

PI always uses only the highest quality Grade 0 CCD devices in order to ensure the best performing quantitative detectors in the industry.

To assist customers in understanding the grading process, we've provided the definitions below, as well as a few examples to compare grading between manufacturers.

Central Zone:
The central zone is an area in the middle of the CCD array. The exact location and size varies with the manufacturer. Defects in this region are usually specified separately from the overall number of defects.

Neighborhood:
This is the group of pixels surrounding the defect in question, usually 10,000 pixels or less. Again, the exact specification is manufacturer-specific.

Point Defect:
A point defect is a pixel whose response differs by ±N% compared to the mean values of all pixels in the neighborhood. "N" can be as low as 6% or as high as 20% depending on the manufacturer.

Cluster Defect:
This is a group of adjacent point defects. The maximum allowable number of defective pixels in a cluster varies between 3 and 9, depending on the manufacturer.

Column or Row Defect:
A column or row defect refers to a column or row, or partial column or row, whose response varies by at least ±N% from the neighborhood mean value. "N" is usually the same number as for point defects.

Charge Trap:
A trap is a pixel that traps charge during the charge-transfer process. Charge transfers out of the trap at a lower rate, leading to charge being "left behind." Once a trap is filled, a steady state is reached where it no longer consumes signal electrons. Some manufacturers give specifications for both the number of low-level traps (filled with typically <2000 e-) and high-level traps (filled with typically <10,000 e-). The physical location of the trap is also important, particularly for low-light applications. Traps in the serial register of the CCD can affect signal from nearly the entire sensor. Traps in a column only affect that column's signal. Traps are often quite dependent on the CCD's operating temperature.

Hot Defects:
Some defects (pixel, cluster, or column) are substantially brighter than adjacent regions. Often, this is due to higher-than-average dark current. These defects tend to disappear as the device is cooled. Because their location and dark current rate are constant, they can often be compensated for by dark current subtraction.

CCD Manufacturer E2V Kodak Atmel

CCD CCD30-11 KAF1400 TH7896M

Grade 1 Specs. (max. number in total)

Point Defects 10 hot pixels 5 25

Cluster Defects
3 dark cluster (<3 pixels)
2 dark cluster (<5 pixels
0 3

Column Defects 1 dark, 0 white 0 0

Trap Defects 2 1 0

Grade 2 Specs. (max. number in total)

Total Defects 15 hot pixels
15 dark cluster (<3 pixels) 10 75

Cluster Defects
8 dark cluster (<5pixels)
1 dark cluster (<10 pixels)
4 8

Column Defects 6 black, 0 white 2 4

Trap Defects 5 2 4

This table compares some of the defect specifications for a few popular CCD arrays. The defect amounts are defined by the manufacturer in terms of number of pixels, columns, or clusters whose response differs by ±N%. The deviation, N, is defined independently by each CCD manufacturer and definitions vary widely. Contact us for the exact definitions of the device you are considering.

Dual CCD Readout can be very convenient when the object of your research is as bright as a plasma arc or as dim as a single photon emission event. Or perhaps you routinely perform low-light Raman measurements and must simultaneously characterize the quality of your laser line: two applications with drastically different light conditions. Normally, strong ND filters or two separate detectors would be used for different target applications, but this is no longer necessary. PI/Acton has developed a high-performance camera platform which can be used in a broad range of light conditions.

Hybrid Sensor Technology
Imagine a detector that combines near 100% quantum efficiency, speed independent sub-electron readout noise and negligible dark current with virtually unlimited dynamic range; a non-aging sensor technology that provides the ability to take true quantitative measurements, while giving the ultimate in detection capabilities. Imagine no longer; it’s a reality!

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Hybrid Sensor Technology
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Introduction to Image Intensifiers for Scientific Imaging

An image intensifier is a vacuum tube device, generally 18-25 mm in diameter. The intensifier (see Figure 1) comprises a photocathode input, which is a coating of multi-alkali or semiconductor layers on the inside of the input window, and a phosphor screen, which is a fluorescing phosphor coating on the inside of the output window. Also included are either simple grid-shaped electrodes (i.e., early intensifier technology) to accelerate electrons through the tube or, in later intensifiers, a complex electron-multiplying microchannel plate (MCP) (Figure 2).

A portion of the incident photons striking the photocathode causes electrons to be released via the photoelectric effect. These electrons are then accelerated and multiplied to the phosphor screen, where they strike the output phosphor coating and cause it to release light. This released light consists of many photons for every incident light photon striking the photocathode surface.

View the complete Tech Note:
Introduction to Image Intensifiers for Scientific Imaging
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> spectroscopy Systems

spectroscopy Systems

Key Advantages of PI CCDs - Dual CCD Readout

PI’s PIXIS and SPEC-10 detectors offer a unique CCD architecture with dual readout amplifiers. One amplifier is optimized for very bright light conditions and can handle a full well capacity of typically 1 Me- with a read-noise of 10e- RMS. This is known as a “high capacity amplifier.” The “low noise amplifier” is designed for extremely low light applications. It has a 250k e- full well capacity, but offers a miniscule read-noise of 2.5..3.5 e- RMS. PI is the only manufacturer of spectroscopic CCD systems to offer a user-selectable dual capacity readout. The amplifier type can easily be chosen from the WinSpec software menu.

The diagram below shows the horizontal register and amplifier configuration of the CCD:

Low Noise amplifier High Capacity amplifier

250k e- capacity
Read noise =2..4 e- (typical) 1 Me- capacity
Read noise = 10 e- rms (typical)

In normal operation, light is focused on the CCD imaging area with a typical size of 1340x100 or 1340x400 pixels. After each exposure, signal is shifted from the CCD imaging area downward, consolidating the charge from a whole column of pixels into a single pixel of the Horizontal Shift Register. The two amplifiers are located at each end of the Horizontal Register. The charge can be shifted left to the low noise amplifier, or right to the high capacity amplifier.

The low noise amplifier located to the left is a state-of-the-art design intended to push the limits of ultra-low read noise. It can be used to detect signal consisting of just a few photons. On the other hand its maximum detectable signal before saturation is about 250k e, making it a very versatile device.

The high capacity amplifier located at the right side can achieve a full capacity of about 1Me-. With a one million electron capacity and 10 electron read noise, this amplifier can theoretically attain 100,000: 1 dynamic range. However, the achievable range is roughly 65,000, which is limited by the 16-bit architecture of the amplifier. The High Capacity amplifier is well suited to applications requiring low photon shot noise percentage, e.g., absorption spectroscopy at low O.D. levels and Raman spectroscopy with high fluorescent background.

> spectroscopy > Fluourescence

Fluourescence

Using Planar Laser-Induced Fluorescence To Study Plasma Turbulence
The successful development and optimization of fusion power sources will depend largely upon learning more about plasma turbulence and its relation to transport. Gaining a greater knowledge of plasma-edge turbulence is key, as the transport of particles near the plasma's edge has a profound effect on global plasma confinement. It is in this region that the boundary values for plasma temperature and density are established, values from which internal gradients are subsequently determined. Unfortunately, theories often fail to predict transport under turbulent conditions. Researchers have now begun to utilize high-performance intensified CCD (ICCD) cameras for innovative studies designed to evaluate the potential of using planar laser-induced fluorescence (PLIF), an optical diagnostic technique, for the experimental visualization of plasma-edge turbulence. It is hoped that data acquired via PLIF imaging will lead to improved turbulencetransport
models. This note discusses the recent work of Fred M. Levinton (Nova Photonics, Inc., Princeton, NJ) and Fedor Trintchouk (Princeton Plasma Physics Laboratory, Princeton, NJ).

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Using Planar Laser-Induced Fluorescence To Study Plasma Turbulence
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> spectroscopy > NIR spectroscopy

NIR spectroscopy

MonoVista CRS

Raman Spectroscopy Basics
Raman Spectroscopy is a spectroscopic technique based on inelastic scattering of monochromatic light, usually from a laser source. Inelastic scattering means that the frequency of photons in monochromatic light changes upon interaction with a sample. Photons of the laser light are absorbed
by the sample and then reemitted. Frequency of the reemitted photons is shifted up or down in
comparison with original monochromatic frequency, which is called the Raman effect. This shift
provides information about vibrational, rotational and other low frequency transitions in molecules.
Raman spectroscopy can be used to study solid, liquid and gaseous samples.

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Raman spectroscopy Basics
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> spectroscopy Systems > TriVista CRS

TriVista CRS

> Spectrographs & Monochromators > TriVista - Triple Spectrometer

TriVista - Triple Spectrometer

> Scientific Imaging

Scientific Imaging

Kinetics Readout for Fast Temporal Studies
Most of the Princeton Instruments cameras -including the new PIXIS CCD line and the PhotonMAX EMCCD line of cameras - support the kinetics operation. The feature is attractive to Bose-Einstein Condensate (BEC) community as well as researchers interested in capturing transient events at microsecond time scale. Aided by the back illumination technology for high QE and multiplication gain for sub-electron read noise, the kinetics mode in PhotonMAX provides the powerful combination of speed and sensitivity. The technical note describes the kinetics mode operation in PhotonMAX: 512B EMCCD cameras as implemented in WinView and WinSpec software packages (ver. 2.5.19.4 or later). However, the concept can be applied, albeit as a simpler case, to other PI CCD cameras such as PIXIS.

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Kinetics Readout for Fast Temporal Studies
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